Humid highland forest enclaves are remnants of Atlantic Forest found in tablelands within the Caatinga biome (Northeastern Brazil), which emerged during interglacial periods in the Pleistocene. These ecosystems have a highly diverse and endemic fish fauna. Most earlier surveys have focused on the tableland of Borborema (Pernambuco and Paraíba States). In this study we surveyed the fish fauna of the humid forest enclaves in the tablelands of Ibiapaba and Araripe, based on samples collected in the rainy season (March and April) between 2009 and 2014. The 45 sampling points covered rivers, streams and reservoirs in five river basins belonging to three ecoregions. The species were listed according to drainage divide, and endemism was determined for each ecoregion and for the Caatinga. Our area was more species-rich (n=59) than Borborema (n=27). The samples included five introduced species and 29 species endemic to the Caatinga (49.1% of the sampled species). The distribution of Parotocinclus haroldoi was expanded to the Mid-Northeastern Caatinga ecoregion (Timonha river basin, Ceará State). Our study intends to make a significant contribution to current knowledge of the ichthyofauna in humid highland forest enclaves of semiarid Northeastern Brazil, identified as a priority in the conservation of the biodiversity in the Caatinga.

Few studies have been published on the taxonomy, biology and ecology of the fish fauna of the rivers and reservoirs from the Brazilian Caatinga. Considering the importance of fish surveys as subsidies for future studies and fishing resources management, the purpose of the present study was to assess the fish assemblage of the two largest reservoirs in the middle Acaraú river basin, the Paulo Sarasate and the Edson Queiroz reservoirs, state of Ceará, Northeastern Brazil. Eight nycthemeral samplings were performed with gillnets (mesh size ranging from 3 to 12 cm between opposite knots) during rainy and dry season between 2010 and 2012. We captured 1,626 specimens belonging to three orders, nine families and 17 species, six of which are endemic to the Caatinga. Approximately 30% of the species observed were non-native and had been introduced for stocking purposes.

No abstract

Aim:To evaluate possible nycthemeral and seasonal temporal patterns in fish assemblage associated with limnological aspects and biotic factors in two reservoirs in semarid Northeastern Brazil.MethodsFish were sampled with gillnets in nycthemeral cycles throughout the dry and rainy season in two reservoirs (Paulo Sarasate/PS and Edson Queiroz/EQ). The stomach contents of the predator species were surveyed. The limnological variables were submitted to principal components analysis, while their relation to fish abundance was determined by canonical correspondence analysis. Temporal patterns in relative fish species abundance were detected with nMDS.ResultsTemperature and dissolved oxygen levels segregated the reservoirs physico-chemically. Turbidity and chlorophyll-a levels differed between seasons, and the relative abundance of species differed between the reservoirs. Predators were more abundant in PS, while detritivores were more abundant in EQ. Triportheus signatusand Plagioscion squamosissimus were the most abundant species in both reservoirs. In general, predator abundance was positively associated with high temperature and dissolved oxygen (PS>EQ) and negatively associated with turbidity. The activity patterns of P. squamosissimus could not be explained by fluctuations in environmental variables. Non-predators tended to cluster around the vectors chlorophyll-a, pH and turbidity. Predators had a more diversified diet in PS in accordance with food availability, while predators in EQ ate only fish and shrimp. Nycthemeral patterns varied for the same species depending on the reservoir. Generally, in PS predators were more active during daylight hours while non-predators were more active after dark. However, in EQ predators and non-predators displayed similar nycthemeral activity patterns. Regardless of the reservoir, predators were more abundant in the rainy season. No seasonal trend was observed for non-predators.ConclusionsLimnological differences between PS and EQ influenced temporal species abundance patterns. The species distribution was determined by predation conditions and physiological attributes.

The relationship between functional and taxonomic diversity is a major issue in ecology. Biodiversity in aquatic environments is strongly influenced by environmental gradients that act as dispersion and niche barriers. Environmental conditions act as filters to select functional traits, but biotic interactions also play a role in assemblage structure. In headwater streams, the relationship between functional and taxonomic diversity remains unclear. In this study we investigated how environmental conditions, taxonomic diversity and biotic interactions influence the spatial distribution of traits and functional diversity in stream fish species. Standardized sampling of fish species was carried out in 50 m sections of 16 streams located in rainforest enclaves in a semiarid region of Brazil (Caatinga biome). The functional diversity indices displayed different responses to the predictor variables used. Functional richness was mainly influenced by environmental conditions, while functional evenness was mostly determined by taxonomic diversity. On the other hand, functional dispersion was explained by a combination of environmental conditions and taxonomic diversity. The spatial distribution of fish species with the same functional traits was random, indicating that biotic interactions are not a strong predictor in these ecosystems. Channel width, pH and substrate were the most important variables in the spatial distribution of the functional traits of the fish species. Our results suggest that the functional structure of fish assemblages in headwater streams depends mainly on environmental conditions and taxonomic diversity.

Environmental and spatial factors are known as the main determinants of community variation in aquatic organisms. However, historical factors may interact with local processes to regulate community structure patterns. Here we compared historical, environmental, and spatial factors in a multi-scale approach in order to identify the main drivers structuring species composition and functional diversity of fish communities in forest enclaves across three hydrographic basins in semiarid Brazil Caatinga biome. We initially modeled spatial structure within each basin using asymmetric eigenvector maps (AEM). We then partitioned the explanation of the variation in local community structure into three groups of predictor variables: (1) environmental variables, (2) spatial variables, and (3) phylogenetic history. Biogeographical bias was assessed using a basin identity matrix as covariable. The combination of 1, 2, and 3 explained the variation in species composition, while pure spatial, phylogenetic, and environmental components explained the distribution of functional groups and their nested patterns. Our findings confirmed the importance of phylogenetic history, as well as the usefulness of robust methods in community studies in refining explanations of the processes determining variation in species composition and functional groups.

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large‐scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.

No abstract